NASA's Johnson Space Center has signed an agreement with MSE Technology Applications to collaborate in the development of advanced rocket technology that could halve the eight-month journey time to Mars in the next decade.
The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) technology is being developed at Johnson's Houston, Texas-based Advanced Space Propulsion Laboratory, headed by former Shuttle astronaut and applied plasma physicist and fusion technologist Franklin Chang-Diaz.
The electrical conducting properties of plasma - an ionised, electrically charged gas made up of atoms stripped of some of their electrons - allows the plasma to be guided and accelerated by properly designed magnetic fields. The VASIMR engine comprises three linked magnetic cells - the first cell handles the main injection of propellant gas and its ionisation, the central cell acts as an amplifier to further heat the plasma and the aft cell is a magnetic nozzle, which converts the energy of the fluid into directed flow.
Neutral gas, typically hydrogen, is injected into the forward cell and ionised. The resulting plasma is electromagnetically energised in the central cell by ion cyclotron resonance heating, in which radio waves give their energy to the plasma, heating it in a manner similar to the way a microwave oven works. After heating, the plasma is magnetically exhausted at the aft cell to provide modulated thrust, with the magnetic nozzle of the cell converting the energy of the plasma into a velocity vector. A key to the technology is the capability to modulate the plasma exhaust to maintain optimal propulsive efficiency, says NASA.
On a mission to Mars, this type of rocket could continuously accelerate through the first half of its journey and reverse its attitude and slow down during the second half of the voyage. This could cut the Mars journey time from seven to eight months down to just over three months. The technology may have commercial applications, with a variable-exhaust plasma rocket offering operational flexibility in the positioning of satellites in Earth orbit, says NASA.
Source: Flight International
